Latest content added for UNT Digital Library Partner: UNT Librarieshttp://digital.library.unt.edu/explore/partners/UNT/browse/?fq=str_degree_discipline:Chemistry&fq=untl_collection:UNTETD2014-03-26T18:36:44-05:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Partner: UNT LibrariesStoichiometry and Deposition Temperature Dependence of the Microstructural and Electrical Properties of Barium Strontium Titanate Thin Films2014-03-26T18:36:44-05:00http://digital.library.unt.edu/ark:/67531/metadc279410/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc279410/"><img alt="Stoichiometry and Deposition Temperature Dependence of the Microstructural and Electrical Properties of Barium Strontium Titanate Thin Films" title="Stoichiometry and Deposition Temperature Dependence of the Microstructural and Electrical Properties of Barium Strontium Titanate Thin Films" src="http://digital.library.unt.edu/ark:/67531/metadc279410/thumbnail/"/></a></p><p>Barium Strontium Titanate (BST) was deposited on Pt/ZrO2 / SiO2/Si substrates using liquid source metal organic chemical vapor deposition. A stoichiometry series was deposited with various GrII/Ti ratios (0.658 to 1.022) and a temperature series was deposited at 550 to 700°C. The thin films were characterized using transmission electron microscopy.
Both series of samples contained cubic perovskite BST and an amorphous phase. The grain size increased and the volume fraction of amorphous phase decreased with increasing deposition temperature. The electrical and microstructural properties improved as the GrII/Ti ratio approached 1 and deteriorated beyond 1. This research demonstrates that BST thin films are a strong candidate for future
MOS transistor gate insulator applications.</p>Survey of the Solid State Conformation of Calix[4]arenes2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278942/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278942/"><img alt="Survey of the Solid State Conformation of Calix[4]arenes" title="Survey of the Solid State Conformation of Calix[4]arenes" src="http://digital.library.unt.edu/ark:/67531/metadc278942/thumbnail/"/></a></p><p>The characteristics of seventy-six calix[4]arene crystal structures derived from the Cambridge Crystallographic Database are presented. This survey is a discussion of the
inter and intramolecular effects on the solid state cavity shape and molecular recognition ability of the compounds. In addition to this survey, four new calix[4]arene crystal structures are presented. The conformational characteristics
of these four calixarenes are determined by a complicated array of inter and intramolecular interactions in the crystal packing.</p>Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278914/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278914/"><img alt="Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study" title="Interactions of Clean and Sulfur-modified Reactive Metal Surfaces with Aqueous Vapor and Liquid Environments : A Combined Ultra-high Vacuum/electrochemistry Study" src="http://digital.library.unt.edu/ark:/67531/metadc278914/thumbnail/"/></a></p><p>The focus of this research is to explore the molecular-level interactions between reactive metal surfaces and aqueous environments by combined ultra-high vacuum/electrochemistry (UHV-EC) methodology. The objectives of this work are to understand (1) the effects of sulfate ions on the passivity of metal oxide/hydroxide surface layer, (2) the effects of sulfur-modification on the evolution of metal oxide/hydroxide surface layer, and (3) the effects of sulfur adsorbate on cation adsorption at metal surfaces.</p>Chemical Equilibria in Binary Solvents2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278936/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278936/"><img alt="Chemical Equilibria in Binary Solvents" title="Chemical Equilibria in Binary Solvents" src="http://digital.library.unt.edu/ark:/67531/metadc278936/thumbnail/"/></a></p><p>Dissertation research involves development of Mobile Order Theory thermodynamic models to mathematically describe and predict the solubility, spectral properties, protonation equilibrium constants and two-phase partitioning behavior of solutes dissolved in binary solvent mixtures of analytical importance. Information gained provide a better understanding of solute-solvent and solvent-solvent interactions at the molecular level, which will facilitate the development of better chemical separation methods based upon both gas-liquid and high-performance liquid chromatography, and better analysis methods based upon complexiometric and spectroscopic methods. Dissertation research emphasizes chemical equilibria in systems containing alcohol cosolvents with the understanding that knowledge gained will be transferable to more environmentally friendly aqueous-organic solvent mixtures.</p>Mobile Order Theory as Applied to Polycyclic Aromatic Heterocycles2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278994/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278994/"><img alt="Mobile Order Theory as Applied to Polycyclic Aromatic Heterocycles" title="Mobile Order Theory as Applied to Polycyclic Aromatic Heterocycles" src="http://digital.library.unt.edu/ark:/67531/metadc278994/thumbnail/"/></a></p><p>Experimental mole fraction solubilities of benzil, thianthrene, trans-stilbene, thioxanthen-9-one, diphenyl sulfone and dibenzothiophene sulfone are determined in pure noncomplexing and complexing solvents. Predicted solubility values are calculated for benzil, thianthrene, trans-stilbene and thioxanthen-9-one using expressions derived from Mobile Order theory. Large deviations between experimental and predicted solubilities in alcohol solvents exist, therefore optimized solute - solvent association constants are determined. Previously measured thianthrene solubilities in five binary alkane + cyclohexane solvent mixtures are compared with values predicted from Mobile Order theory using the measured solubility in each of the pure solvents as input parameters. The experimental mole fraction solubility of benzil in eight binary alcohol + 1-octanol solvent mixtures are also measured and compared with predicted values.</p>Kinetics and Mechanisms of Metal Carbonyls2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278709/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278709/"><img alt="Kinetics and Mechanisms of Metal Carbonyls" title="Kinetics and Mechanisms of Metal Carbonyls" src="http://digital.library.unt.edu/ark:/67531/metadc278709/thumbnail/"/></a></p><p>Pulsed laser flash photolysis with both visible and infrared detection has been applied to the study of the displacement of weakly coordinating ligands (Lw) by strongly "trapping" nucleophiles (Ls) containing either an olefinic functionality (Ls = 1-hexene, 1-decene, 1-tetradecene) or nitrogen (Ls = acetonitrile, hydrocinnamonitrile) from the photogenerated 16 electron pentacarbonylchromium (0) intermediate. 5-Chloropent-l-ene (Cl-ol), a potentially bidentate ligand, has been shown to form (ol-Cl) pentacarbonylchromium (0), in which Cl-ol is bonded to Cr via a lone pair on the chlorine, and isomerize to (Cl-ol) pentacarbonylchromium (0), in which Cl-ol is bonded to the olefinic functionality
on the submillisecond time scale. This process has been studied in both the infrared and visible region employing both fluorobenzene or n-heptane as the "inert" diluent. Parallel studies employing 1-chlorobutane and 1-hexene were also evaluated and showed great similiarity with the Cl-ol system. The data supported a largely dissociative process with a possibility of a small interchange process involving the H's on the alkyl chain. Studies were also carried out for various Cr(CO)6/arene/Ls systems (arene = various alkyl or halogenated substituted benzenes). The data indicated that for both C6H5R (R=various
alkyl chains) or multi-alkyl substituted arenes (i.e. o-xylene, 1,2,3-trimethylbenzene) containing an "unhindered" ring-edge, bonding to the the Cr(CO)5 moiety occurs "edge on" via a partially delocalized center of unsaturation on the ring. The data indicated that both electronic and steric properties of the arenes influence the kinetics, and that an interchange pathway takes place at least, in part, through the alkyl chains on both the arenes and "trapping" nucleophiles. Moreover, halogenated arenes bond through the lone pair on the halogen for both CI- and Br- derivatives but "edge-on" for the fluorinated arenes. Finally, in the case of arene complexes without and "unhindered" ring-edge (i.e.,
1,2,3,4,5-pentamethylbenzene) bonding can occur either "edge-on" or through the ring center of the arene or combination of the two. Carbonyl stretching frequencies for the arenes are also indicative of the type of bonding.</p>Syntheses of Antimetabolites2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc279358/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc279358/"><img alt="Syntheses of Antimetabolites" title="Syntheses of Antimetabolites" src="http://digital.library.unt.edu/ark:/67531/metadc279358/thumbnail/"/></a></p><p>In these studies several different types of antimetabolites were synthesized, and their biological effects were examined in various assay systems. More extensive investigations were done in microbial systems in which many of the compounds proved to be inhibitory to growth, and attempts were made to determine the mode of biochemical action by adding supplements of the appropriate natural metabolite.</p>Experimental and Theoretical Studies of Polycarbocyclic Compounds2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc279238/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc279238/"><img alt="Experimental and Theoretical Studies of Polycarbocyclic Compounds" title="Experimental and Theoretical Studies of Polycarbocyclic Compounds" src="http://digital.library.unt.edu/ark:/67531/metadc279238/thumbnail/"/></a></p><p>Part I. Diels-Alder cycloadditions of 1,2,3,4,9,9-hexachloro-1α,4α,4aα,8aβ-tetrahydro-l,4-methanonaphthalene (32) and 1,2,3,4,9,9-hexachloro-lα,4α,6,7- tetrahydro-l,4-methanonaphthalene (33) to 4-methyl- and 4-phenyl-l,2,4-triazoline-3,5-dione [MTAD and PTAD, respectively] and to N-methylmaleimide (NMM) have been studied. The structures of several of the resulting cycloadducts were determined by X-ray crystallographic methods. The observed stereoselectivity of each of these Diels-Alder reactions was further investigated via application of theoretical methods. Thus, semiempirical (AMI) and ab initio molecular orbital calculations were used to calculate relative energies. Ab initio calculations were employed to perform frontier molecular orbital analyses of diene-dienophile interactions.</p>An Approach Towards the Total Synthesis of Clonostachydiol2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278800/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278800/"><img alt="An Approach Towards the Total Synthesis of Clonostachydiol" title="An Approach Towards the Total Synthesis of Clonostachydiol" src="http://digital.library.unt.edu/ark:/67531/metadc278800/thumbnail/"/></a></p><p>The syntheses of the unsymmetrical 14-membered bismacrolides have been reviewed. A total synthesis of clonostachydiol, the latest to join this family, has been attempted using trimethylsilyl acetylene as the builiding block and palladium catalyzed reactions for the formation of key bonds. The alkyne groups were introduced by Stille coupling of trimethylstannylethynyltrimethylsilane with an acid chloride for one fragment and by addition of lithiotrimethylsilyl acetylene to an aldehyde for the other. Lactic acid derivatives were chosen as starting materials for both fragments, thus introducing two of the chiral centers. The remaining stereocenters were introduced using stereoselective reductions of ketones.</p>Magnetic Exchange in Oxovanadium(IV) Complexes with N-Salicylideneamino Acids2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278821/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278821/"><img alt="Magnetic Exchange in Oxovanadium(IV) Complexes with N-Salicylideneamino Acids" title="Magnetic Exchange in Oxovanadium(IV) Complexes with N-Salicylideneamino Acids" src="http://digital.library.unt.edu/ark:/67531/metadc278821/thumbnail/"/></a></p><p>Copper(II) and oxovanadium(IV) ions resemble one another magnetically in having one unpaired electron in their complexes irrespective of their geometrical structures and bond types involved. Copper(II) complexes with antiferromagnetic exchange are well known. On the contrary, antiferromagnetic exchange in oxovanadium(IV) complexes is rather new and not well established. Very few oxovanadium(IV) complexes have been reported to have this anomalous magnetic property. In the investigation of the magnetic properties of oxovanadium(IV) complexes, we have successfully prepared two series of new oxovanadium(IV) complexes with N-salicylideneamino acids.</p>